,open structure ...Makes the bindings in the structures visible in the current package.
The packages associated with the structures will be loaded if
this has not already been done (the ask-before-loading switch
can be used disable the automatic loading of packages).

,config [command]Executes command in the config package, which includes
the module configuration language.
For example, use

,config ,load filename

to load a file containing module definitions.
If no command is given, the config package becomes the
execution package for future commands.

,user [command]This is similar to the ,config. It
moves to or executes a command in the user package (which is the
default package when the Scheme 48 command processor starts).